CodeWarrior is a very powerful and professional IDE. The main feature of CodeWarrior IDE is the source level debugger in assembler and C. 

CodeWarrior IDE works with Serial Monitor firmware.  

Code Warrior does not work with D-Bug12 monitor firmware, but AsmIDE does.  AsmIDE only works with D-Bug12 monitor.

If you use CodeWarrior IDE, your need the Dragon12 board pre-loaded with serial monitor.

If you use AsmIDE or MiniIDE, your need the Dragon12 board pre-loaded with D-Bug12 monitor.

To replace D-Bug12 monitor with serial monitor, you need a BDM POD to perform the task. The procedure to program the on-chip flash memory is provided at: http://www.evbplus.com/TinyBDM_9s12/TinyBDM_9s12.html

The Code Warrior tutorial: http://www.microdigitaled.com/HCS12/HCS12_books.htm

The Code Warrior download:  CodeWarrior IDE 5.1 SE.
Freescale/NXP removed support for the MC9S12DG256 which is used in our trainers from the newer 5.2 SE (special edition).
As far as for DG256 development is concerned, there is no difference between 5.1 and 5.2.

So the 5.1 SE is still the most popular IDE for the MC9S12DG256.